Trials and tribulations in the first three years in operation of the SSAMS for biomedical ¹⁴C-AMS at LLNL

Journal Article · 16 May 2018 · Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms

DOI: https://doi.org/10.1016/j.nimb.2018.05.008 · OSTI ID:1488813

Ognibene, T. J. ^[1]; Haack, K. W. ^[1]; Bench, G. ^[1]; Turteltaub, K. W. ^[2]

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1. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States). Center for Accelerator Mass Spectrometry
2. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States). Biology and Biotechnology Division

We report on the first several years of operation of our recently installed 250 kV SSAMS at LLNL, purchased to replace our 1-MV AMS system for the measurement of ¹⁴C from labeled biochemical samples. We have modified the ion source region to improve ion output. Additionally, the SSAMS required significant software modifications to the data acquisition system in order to accurately measure ¹⁴C at the high-count rates typically encountered with labeled biochemical samples. Here, we found that the data can be corrected assuming a nonparalyzable dead time response with a single event dead time of 6 µs. Since operation began, we have measured over 13,000 graphitic unknowns and over 1900 standards with an overall precision of 1.0%. We have optimized our system for the analysis of CO₂ gas samples. We compared aliquots of identical samples measured as solid graphite and as liquid drops. Excellent agreement was found between the two, although the average precision of the graphite targets was an order of magnitude better than the liquid drop analysis due to the much larger number of ¹⁴C atoms available for measurement.

• Research Organization: Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)
• Sponsoring Organization: USDOE National Nuclear Security Administration (NNSA)
• Grant/Contract Number: AC52-07NA27344
• OSTI ID: 1488813
• Report Number(s): LLNL-JRNL--741335; 895864
• Journal Information: Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Journal Name: Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms Journal Issue: C Vol. 438; ISSN 0168-583X
• Publisher: ElsevierCopyright Statement
• Country of Publication: United States
• Language: English